1. Field of the Invention
The present invention relates to a slide spool valve, and more particularly, to a slide spool valve, a valve body of which has an improved structure formed using a metallic pattern in an injection molding process, which is advantageous for mass production.
2. Description of the Related Art
As is well known, a slide spool valve includes a valve spool inserted in a bore and changes the flow of compressed air or operating fluid as the valve spool reciprocates along an axial direction in the bore. Since the motion of the valve spool is minimally affected by the pressure of the compressed air or the operating fluid, air or fluid flow can be easily controlled using the slide spool valve. Thus, the slide spool valve has been widely used as a three or more-port connection directional control valve.
FIG. 1 illustrates a conventional slide spool valve, disclosed in U.S. Pat. No. 6,325,102, which is used as a main valve of a directional control valve. Referring to FIG. 1, a valve body 1 comprises a bore 2 and five ports, namely, a supply port P, two load ports A and B, and two exhaust ports R1 and R2. The five ports are spaced at predetermined intervals in an axial direction and each formed by penetrating an inner circumferential surface of the bore 2. A valve room 3 extends from the penetrating portion of each port, which is formed in the inner circumferential surface of the bore 2, and has a diameter larger than a diameter of the bore 2. A valve spool 4, which is inserted in the bore 2, has a plurality of valve portions 5 formed in a flange shape along the valve spool 4 in accordance with the number and spacing of the ports. Each of the valve portions 5 is encompassed by an elastic seal ring 6 to respectively seal the inner circumferential surface of the bore 2. In FIG. 1, reference numeral 7 denotes a bracket for connecting a fitting.
The valve spool 4 is operated by an actuator (not shown) to move in alternate directions in the bore 2. In a normal state, as shown in FIG. 1, the valve spool 4 is in its most right position. When the valve spool 4 is in the normal state, the exhaust port R1 is closed off, the supply port P is connected to the load port A, and the load port B is connected to the other exhaust port R2. When the valve spool 4 moves to the left, the load port A is connected to the exhaust port R1, the supply port P is connected to the load port B, and the exhaust port R2 is closed off.
The actuator for the valve spool 4 can be of various types, for example, a direct driven type using a solenoid and spring, an internal or external pilot operated type, or a solenoid controlled pilot operated valve according to the type of a valve.
The elastic seal rings 6, which respectively encompass the valve portions 5 of the valve spool 4, seal the inner circumferential surface of the bore 2. If the elastic seal ring 6 is damaged or worn out, the leakage of fluid may occur, causing a malfunction of the slide valve spool. The valve room 3 is required to prevent the elastic seal ring 6 from being damaged by the corner of the penetrating portion of each port connected to the inner circumferential surface of the bore 2. Without the valve room 3, the entire elastic seal ring 6 cannot be uniformly pressurized around the penetrating portion of each port and is loosened toward the penetrating portion of each port. Thus, the loosened portion of the elastic seal ring 6 may be caught by the corner of the penetrating portion and be damaged or detached.
In the slide spool valve, the valve room 3 is required to protect the elastic seal ring 6 from damage, but the structure of the valve room 3 makes it hard to form the valve body by synthetic resin injection molding. Also, the valve body 1 cannot be formed of iron, which erodes due to moisture or the like. Thus, a conventional slide spool valve comprises a valve body manufactured by aluminum die casting.
As described above, a valve body of a conventional slide spool valve is manufactured by aluminum die casting and a valve room in a bore is secondarily processed so that the manufacture thereof is difficult and the cost is high.